/*
 * Base64URL-ArrayBuffer
 * https://github.com/herrjemand/Base64URL-ArrayBuffer
 *
 * Copyright (c) 2017 Yuriy Ackermann <ackermann.yuriy@gmail.com>
 * Copyright (c) 2012 Niklas von Hertzen
 * Licensed under the MIT license.
 * 
 */
(function(){
    "use strict";

    var chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_";

    // Use a lookup table to find the index.
    var lookup = new Uint8Array(256);
    for (var i = 0; i < chars.length; i++) {
        lookup[chars.charCodeAt(i)] = i;
    }

    var encode = function(arraybuffer) {
        var bytes = new Uint8Array(arraybuffer),
        i, len = bytes.length, base64 = "";

        for (i = 0; i < len; i+=3) {
            base64 += chars[bytes[i] >> 2];
            base64 += chars[((bytes[i] & 3) << 4) | (bytes[i + 1] >> 4)];
            base64 += chars[((bytes[i + 1] & 15) << 2) | (bytes[i + 2] >> 6)];
            base64 += chars[bytes[i + 2] & 63];
        }

        if ((len % 3) === 2) {
            base64 = base64.substring(0, base64.length - 1);
        } else if (len % 3 === 1) {
            base64 = base64.substring(0, base64.length - 2);
        }

        return base64;
    };

    var decode = function(base64) {
        var bufferLength = base64.length * 0.75,
        len = base64.length, i, p = 0,
        encoded1, encoded2, encoded3, encoded4;

        var arraybuffer = new ArrayBuffer(bufferLength),
        bytes = new Uint8Array(arraybuffer);

        for (i = 0; i < len; i+=4) {
            encoded1 = lookup[base64.charCodeAt(i)];
            encoded2 = lookup[base64.charCodeAt(i+1)];
            encoded3 = lookup[base64.charCodeAt(i+2)];
            encoded4 = lookup[base64.charCodeAt(i+3)];

            bytes[p++] = (encoded1 << 2) | (encoded2 >> 4);
            bytes[p++] = ((encoded2 & 15) << 4) | (encoded3 >> 2);
            bytes[p++] = ((encoded3 & 3) << 6) | (encoded4 & 63);
        }

        return arraybuffer;
    };

     /**
     * Exporting and stuff
     */
    if (typeof module !== 'undefined' && typeof module.exports !== 'undefined') {
        module.exports = {
            'encode': encode,
            'decode': decode
        }

    } else {
        if (typeof define === 'function' && define.amd) {
            define([], function() {
                return {
                    'encode': encode,
                    'decode': decode
                }
            });
        } else {
            window.base64url = {
                'encode': encode,
                'decode': decode
            }
        }
    }
})();